Annie Lennox’s follow up to Walking On Broken Glass wasn’t as successful…
Anyway, is there anything you can take a leak on that will cause bodily damage from the act of pissing on it? The only thing I can think of is something with live electrical current or in the Amazon river where that fish swims up your urethra.
Are there any others?
Try pissing on the meanest and toughest looking guy on the street and see what happens. 
Well you never know, he might be into it!
A lump of sodium or potassium (or any other water reactive substances for that matter) would at least give you a surprise, if not something much more substantial.
Certain masses of Corium—if only because to be close enough to piss on it, you’d receive a lethal radiation dose in under a minute.
How about a pool of a liquified poisonous gas in a cold room, like say phosgene (BP 46.9 F), that you cause to boil by pissing in it. I’m not sure it would all that safe to be standing around near a liquid puddle of phosgene in the first place, though.
How about Calcium Carbide… while smoking.
Water + CaC gives of C2H2 … which is quite an explosive gas.
If your urine contains too much ammonia (possible with some infections) and you pee into bleach you will make deadly chlorine gas.
You’d actually make Chloramine, which is still nasty, but not quite as bad as Chlorine.
You do know that this would be impossible because of simple fluid physics?
Antimatter would do it. You wouldn’t even need very much of it for your urine to obliterate yourself and everything else in the room.
You mean to tell me that the TV lied to me?!
Thanks for the replies; there’s a lot I’ve forgot from high school chemistry evidently.
Concentrated sulfuric acid would boil violently and could easily splash back on you and burn your skin. (There are probably several other strong acids or alkalies that would also do this.)
Anything sufficiently hot to boil the urine, and in particulate or liquid form, could also cause splashback, and if it were dangerous on skin contact could thereby harm you. Some sorts of actual radioactive waste might meet these criteria (though it it were radioactive enough to spontaneously heat itself to a temperature that could boil urine, just standing close to it would probably be enough to kill you anyway).
Cecil did two columns about the candiru fish. The second one has different documentation, and apparently confirms the dreadful folklore. There’s a link at the end of Cecil’s piece that shows photos, as well as rather detailed description of removal from one victim.
Simple fluid dynamics makes it impossible for a fish in a river to swim up the stream of someone pissing from the open air. It doesn’t preclude the fish from swimming into the urethra of a wader or swimmer whose urinary equipment is already submerged.
Just to address this part: this is probably safer than you think. The current is going to want a solid stream of urine for there to be any danger of electrocution. The reality is that urine pretty quickly separates into droplets rather than a continuous stream. You’d need a higher volume of water than a human can product to have a solid stream of urine all the way to the ground… or you’d need to be really close to the electrical source. Heck, even the water flow from a garden hose breaks up into separate globules of water within a few feet.
:dubious: Really? That is certainly not how it looks, when pissing from a normal height (and assuming one has more that a tiny amount to do).
Mythbusters did an episode on this one. It’s probably somewhere on YouTube.
Part of the issue is that the stream is moving pretty quickly. Your eye connects the dots, so to speak.
Ah, here it is - the myth that someone died taking a piss on an rail track they called busted. While there are several idiots who claim to be pissing on an electric fence the could just be acting, but there’s also a vid of a dog cocking its leg at an electric fence which definitely gets a shock and anatomically I wouldn’t think stream of doggy wee is all that different to human.
Pissing on nitroglycerin seems like a pretty bad idea.